In aircraft, fuel pumps are conventionally driven in their operation by power taken from the aircraft engine and delivered through a gearbox to a mechanical coupling that in turn provides an input to the fuel pump. It has been found to be desirable in the arrangement just described that the mechanical coupling be provided with a means to lubricate the ends of the coupling that respectively engage the gearbox and the pump. The gearbox has a limited supply of lubricant contained therein, which lubricant is delivered under pressure to the various bearing components of the gearbox. Historically this supply of lubricant has been delivered to either end of the mechanical coupling that joins the gearbox and the pump by passages in the coupling that delivers lubricant from the gearbox to the pump. Return passages in the coupling are provided to allow the return of lubricant from the pump to the gearbox. In the event of a bearing failure in the pump or the ingestion of a foreign object into the pump, either of which can cause the pump to jam, the mechanical coupling experiences an overload and fails in torsional shear. This failure is rapidly followed by the loss of gearbox lubricant through the passages in the coupling which is in a state of rupture. The gearbox, absent lubricant fails next in what may result in a cascading, compounding series of failures of other aircraft components that depend upon continued gearbox integrity.
The invention to be described hereinafter completely solves the problem defined next above.
The problem of fluid loss from a fluid line where the fluid line is involved in a suddenly appearing destructive environment has been addressed in U.S. Pat. No. 3,963,055 issued to J. DeRosa. The DeRosa patent is directed to a self sealing fuel line wherein the fuel line is comprised of lengths of hard material having a relatively high tensile strength interrupted by rings of soft ductile material. When the fuel line is subjected to an impact or excessive forces sufficient to cause rupture, the ductile rings are first drawn to a relatively small diameter, pinching off an inner resilient seal tube to shut off further flow. The DeRosa patent offers no suggestion of a mechanical coupling wherein an inner lubrication tube is twisted to the point of rupture thereby reducing the inner diameter of the tube and preventing fluid loss from the ruptured tube, such as the invention to be discussed hereinafter provides.